Minister for Enterprise Richard Bruton has described allegations that Washington spied on the European Union and other allies as "very disconcerting" but insisted clarification on what exactly took place is still needed.

Speaking in Limerick today, Mr Bruton said EU-US negotiations on a free trade agreement had enormous potential for economies on both sides of the Atlantic but only if they were conducted on a fair basis.

“Clearly it’s very disconcerting but I think we need to wait full clarification,” Mr Bruton said. “ I think we have to await clarification but I remain of the belief that we need good strong negotiations but it has to be on a fair basis.”

The EU has strongly demanded that the United States explain a report that Washington is spying on the group, saying that, if true, the alleged surveillance was "shocking".

Former EU ambassador to the United States John Bruton yesterday said it was in the interest of the US to "come clean, completely and immediately'' on the bugging allegations.

“It must also give assurances that this sort of behaviour will never be tolerated again,’’ he added.

Mr Bruton, a former taoiseach, who served as ambassador between 2004 and 2009, said he would be very concerned if the allegations were true, because the EU, representing 27 countries and 500 million people, had been working very closely and on a trusting basis with the US.

“We put our cards on the table and we hope and expect them to do the same in negotiations,’’ he added. “And if they are seeking to take an unfair advantage by accessing surreptitiously, and in effectively a hostile way, our internal communications, that, I think, upsets the balance of the relationship in a very damaging way.”

Mr Bruton said his Washington office was involved in “pretty sensitive negotiations’’ with the US on issues such as access for airlines to US airports, data privacy and the different positions being taken on the world trade talks.